Childbirth includes both labor (the process of birth) and delivery (the birthitself); it refers to the entire process as an infant makes its way from thewomb down the birth canal to the outside world. The average length of laboris about 14 hours for a first pregnancy and about eight hours in subsequent pregnancies. However, many women experience a much longer or shorter labor.

Childbirth usually begins spontaneously, following about 280 days after conception, but it may be started by artificial means if the pregnancy continues past 42 weeks gestation. One of the first signs of approaching childbirth maybe a "bloody show," the appearance of a small amount of blood-tinged mucus released from the cervix (the opening of the uterus) as it begins to dilate. This is called the "mucus plug." In about 10% of women, labor is signaled by the rupture of the amniotic sac. When a woman's "water breaks, " the amniotic fluid is released in a trickle or gush.

The most common sign of the onset of labor is contractions, or labor pains. Sometimes women have trouble telling the difference between "true" and "false"labor pains. True labor pains are felt high up on the abdomen, radiating tothe lower back, and get progressively stronger, longer, and closer together.

Labor can be described in terms of a series of stages. During the first stageof labor, the cervix dilates (opens) from 0-10 cm. This stage has an early,or latent, phase and an active phase. As labor begins, the muscular wall of the uterus begins to contract as the cervix relaxes and expands. During a contraction, the infant experiences intense pressure that pushes it against the cervix, eventually forcing the cervix to stretch open. At the same time, the contractions cause the cervix to thin. Most women are relatively comfortable during the initial latent phase and walking around is encouraged, since it naturally stimulates the labor process.

The active phase of labor is faster and more efficient than the latent phase.Contractions are longer and more regular, usually occurring about every twominutes. They are also more painful. Women may use the breathing exercises learned in childbirth classes to cope with the pain experienced during this phase. Many women also receive pain medication at this point -- either a short-term medication, such as Nubain or Numorphan, or an epidural anesthesia that numbs the lower part of the body.

As the cervix dilates to 8-9 cm, the transition phase begins. This is the transition between the first stage (during which the cervix dilates from 0-10 cm) and the second stage (during which the baby is pushed out through the birthcanal) of labor. The baby's head begins to descend, and the mother begins tofeel the urge to "push" or bear down. Active pushing by the mother should not begin until the second phase, since pushing too early can cause the cervixto swell or to tear and bleed.

As the mother enters the second stage of labor, her baby's head appears at the top of the cervix. The infant passes down the vagina, helped along by strong contractions and the mother's pushing. Active pushing by the mother is veryimportant during this phase of labor.

In some cases, when labor does not progress as it should or the baby appearsto be in distress, a doctor may use forceps or a vacuum extractor to help thebaby out of the birth canal. A forceps is a spoon-shaped device that resembles a set of salad tongs. It is placed around the baby's head so the doctor can pull the baby gently out of the vagina. In vacuum assisted birth, a large rubber or plastic cup is placed against the baby's head, while a pump createssuction that pulls on the cup to ease the baby down the birth canal.

When the top of the baby's head appears at the opening of the vagina, the birth is nearing completion. This position is called crowning, since onlythe crown of the head is visible. As the baby crowns, the perineum (the tissues between the vagina and the rectum) may stretch so tight that the baby's progress is slowed. If there is risk of tearing the perineum, the doctor may choose to make a small incision to enlarge the vaginal opening. This is calledan episiotomy.

Once the baby's entire head is out, the shoulders follow. The attending practitioner suctions the baby's mouth and nose to ease the baby's first breath. The rest of the baby usually slips out easily, and the umbilical cord is cut

In the third and last stage of labor, contractions continue to push the placenta out of the vagina by the continuing uterine contractions. The placenta, which has provided nourishment to the fetus throughout the pregnancy, is pancake shaped and about 10 inches in diameter. It is important that all of the placenta be removed from the uterus to prevent excessive bleeding after childbirth.

Approximately 4% of babies are in what is called the breech position when labor begins. In breech presentation, the baby's bottom or legs are positioned to enter the birth canal instead of the head. Depending on the type ofbreech presentation, the mother and attending practitioner will need to weighthe risks and make a decision on whether to attempt a vaginal birth or deliver the baby with a cesarean section.

A cesarean section, also called a c-section, is a surgical procedure in whichincisions are made through a woman's abdomen and uterus to deliver her baby.Cesarean sections are performed whenever abnormal conditions complicate labor and vaginal delivery, threatening the life or health of the mother or the baby.

There are several popular methods taught to prepare women and their partnersfor childbirth. Lamaze (or Lamaze-Pavlov), introduced in the 1960s, is the most common in the United States today. It promotes breathing exercises and concentration techniques to allow mothers to control pain while maintaining consciousness. Other instructional techniques include the Read method, the LeBoyer method, and the Bradley method.

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